Technical Field
The present disclosure relates to a projective micro-electro-mechanical system (MEMS) device that may be used, for example, for forming a so-called picoprojector of the flying-spot type; further, the present disclosure relates to the related manufacturing method.
Description of the Related Art
As is known, numerous opto-electronic MEMS systems are today available, which are designed to generate images (for example, on corresponding screens) and are characterized by extremely small volumes; these opto-electronic MEMS systems are also known as “picoprojectors”. In general, the volumes of current picoprojectors are so small as to enable inclusion of picoprojectors inside, for example, a cellphone. Picoprojectors may thus form so-called embedded modules of portable electronic devices, such as for example portable PCs, tablets, cellphones, etc.
A picoprojector generally comprises a corresponding projective device, which includes one or more optical sources and may implement different optical techniques.
For instance, the paper by Dawei Rui, et al., “Optical design in illumination system of digital light processing projector using laser and gradient-index lens”, Optical Engineering 51(1) (January, 2012) describes a picoprojector that implements so-called digital light processing (DLP) and includes a plurality of micro-mirrors.
Likewise known are picoprojectors of the flying spot type, which are configured to generate, in use, a corresponding optical beam, the direction of propagation and the spectral composition of which are varied dynamically, for example by a mirror and one or more driving circuits, respectively, so that the optical beam may periodically scan a screen arranged at a distance, thus generating an image thereon. An example of picoprojector of the flying spot type is provided in the paper by Masafumi Ide, et al., “Compact multiple laser beam scanning module for high-resolution picoprojector applications using a fiber bundle combiner”, Advances in Display Technologies IV, Proceedings of SPIE, Vol. 9005, 90050F-1-12.
In general, projective systems of the flying spot type are characterized by overall dimensions smaller than those of projective systems of a DLP type, thanks to the lower complexity.
This having been said, in the field of projective systems of the flying spot type, there is particularly felt the need to improve the optical characteristics of the optical beam generated, without penalizing the overall dimensions. As regards the optical characteristics of the optical beam, they comprise, among other things, power and divergence. In particular, as regards divergence, and assuming an orthogonal reference system xyz, with the axis z coinciding with the axis of the optical beam emitted, it is known that, in the presence of a difference between the divergence of the optical beam in the plane xz and the divergence of the optical beam in the plane yz, the so-called phenomenon of astigmatism arises; i.e., different components of the optical beam focus on different points, reducing the quality of the image generated.